Process for increasing the waterresistance of leather



Unit

PROCESS FOR INCREASING THE WATER- RESISTANCE OF LEATHER No Drawing.Filed June 25, 1958, Ser. No. 744,341

14 Claims. (Cl. 117135.5)

This invention relates to an improved process for rendering leather bothwater-repellent and water-impermeable and more particularly to a methodof rendering leather both water-proof and Water-resistant by a two steptreatment of the leather with (1) aqueous solutions of salts of acidesters having at least two salt forming acyl groups and (2) aqueousalcohol solutions of organic metal complex compounds.

In our previous patent, Plapper et al., US. Patent No. 2,772,988, issuedDecember 4, 1956, we disclose a process for impregnating leather withsolutions which contain organic metal complex compounds which have beenobtained by the reaction of basic polyvalent metal salts with acidphosphoric acid esters of high molecular weight hydroxyl compounds inthe presence of low molecular weight monovalent alcohols. Especiallysuitable are organic complex compounds formed from basic aluminum orchromium salts, which are dissolved in methanol or ethanol, and acidmonoor di-esters of phosphoric acid formed with high molecular weighthydroxyl compounds. These complex compounds produce water-repellent orwater-proofing impregnations when leather is treated therewith.

An object of our invention is to still further improve thewater-impermeability or water-resistance of leather.

A further object of our invention is to improve the penetration of theimpregnation agents and give an easier, more rapid impregnation anduniform distribution of water-proofing agents even in thick leatherssuch as sole leathers.

We have found that the water-impermeability or waterresistance ofleather treated in accordance with US. Patent No. 2,772,988 can besubstantially improved if the leather is pretreated with water-solubleor water-dispersible complex-active organic compounds. Suitablecomplex-active compounds for this purpose are derivatives of di-basic orhigher poly-basic inorganic or organic acids containing hydrophobicradicals or groups which have at least two salt-forming groups capableof forming complexes.

In tabular form our process for impregnating leather is as follows:

(1) Impregnating of leather with a water-miscible derivative of apolybasic acid, said derivative containing at least one hydrophobicradical and at least two saltforming radicals capable of formingcomplexes.

(2) Drying the impregnated leather.

'(3) Impregnating of the leather with a water-miscible, organic complexsalt of a polyvalent metal containing a ratio of at least 2.5 mols of analcohol-soluble, basic States atent C salt of a polyvalent metal withone mol of an acid ester of phosphoric acid esterified with an alcoholcontaining a hydrophobic radical, said alcohol having about 6 to about18 carbon atoms, and having coordinated with said basic salt and saidacid ester a lower molecular weight alcohol.

(4) Drying the impregnated leather.

(5) Further conventional treatment of finishing the leather.

The term hydrophobic group as used herein is well known in the chemicalarts and has been defined by Schwartz and Perry in their publication'Surface Active Agents, Interscience Publishers, Inc., New York (1949),on pages 17-19 as follows:

In View of these considerations it is important to examine some of themore usual types of hydrophobic groups and the ways in which they areobtained.

(1) The straight alkyl chains of eight to eighteen 01' more carbon atomsare derived from the natural fatty acids. These may be used as such ormay be converted to acid chlorides for use in acylation reactions. Theacids or their esters may also be reduced to the corresponding fattyalcohols or through the nitriles to the fatty amines. These in turn canbe used as intermediates in a variety of reactions to introduce the longalkyl chain. The natural fatty acids are possibly the most important rawmaterial for hydrophobic groups. A wider variety of detergents has beenderived from them directly or indirectly, than from any other singlesource.

(2) The lower alkyl groups of three to eight carbon atoms are frequentlyattached to aromatic nuclei such as benzene or naphthalene, thecombination forming a useful type of hydrophobic group. The sources oflower alkyl groups are usually the alcohols. The lower alkyl groups aresometimes used by themselves as hydrophobic groups, as in the case ofthe dialkyl sulfosuccinates:

(3) Certain types of petroleum yield naphthenic acids in the normalcourse of refining. These are surface ac tive in themselves and havealso been used as a source of hydrophobic groups in derived surfaceactive agents. In the refining of petroleum oils by washing withsulfuric acid the surface active petroleum sulfonates are obtained.

In general, organic compounds which we have found to be suitable forthis purpose are derivatives of dibasic or higher polybasic inorganic ororganic acids which contain hydrophobic radicals and at least two free,salt-forming groups capable of combining with the mineral-tanning agentto form an organotnetallic complex grouping. Such polybasic acidderivatives have acid characteristics and are preferably used for thepurpose set forth in the form of their water-soluble salts, especiallythose formed by neutralization with organic bases, their ammonium saltsand alkali metal salts.

Examples of suitable inorganic polybasic acids upon which the abovederivatives are based are boric acid, phosphoric acid, arsenic acid andthe like. Similarly suitable organic polybasic acids are, among others,citric acid, trimesitinic acid, trimellitic 'acid, mellitic acid,diadipic acid, ethane-tetra-acetic acid, sulfophthalic acids,oxyphthalic acids, pyrogallic acid, pyrogallol carboxylic acid, and thelike. Other suitable organic acids are those which contain hydrophobicradicals and may, for example, be obtained by subjecting high molecularweight 1111- .the process according to the invention.

3 saturated fatty acids, fatty alcohols or olefins to a condensationreaction with maleic acid, such as the condensation products of oleicacid, linseed oil fatty acid, soybean oil fatty acid, and the like, withone or several mols of maleic acid. Similarly condensation products suchas alkylated malonic acids are suitable.

While the last mentioned high molecular Weight dior higher polybasiccarboxylic acids may be used as such, the first mentioned trior higherpolybasic inorganic acids or the low molecular weight trior higherpolybasic organic carboxylic acids must be transformed .intocomplexactive compounds .by a partial esterification ,or-a partialamidation with high .molecular weight alcohols or amines which containhydrophobic radicals, and these complex active compounds may then beused in These products are known materials and are readily obtainableaccording to simple procedures. In place of these compounds,

.however, any other .desired compounds which comprise at least twocomplex active salt-forming groups in addition to one hydrophobicradical may also be used.

Examples of some specific complex active compounds "which may be usedfor the purpose according to the invention are the following: aciddodecyl phosphate, acid octadeccnyl phosphate, hexadecyl borate,octadecenyl arsenate, acid hexadecyl citrate, acid dodecylsulfo-'phthalate, citric "acid'mono-octadecyl amide, citric acidmononaphthenyl amide, andthe like, which may be employed as-suchorin theform of their salts.

The hydrophobic radicals of .these compounds may be of an aliphatic,cycloaliphatic, aliphatic-aromatic orali- -''phatic-cycloaliphaticnature, and may be interrupted by oxygen, sulfur and'nitrogen orcarryconstituent radicals containing oxygen, sulfur or nitrogen atoms. Ofparticular interest, for example, are the esters of trior'higher-polybasic organic or inorganic acids formed with "high molecularweight ethoxylated fatty alcohols containing from 1 to mols, preferablyfrom 1 to 3 mols, of ethylene-oxide'per mol of high molecular weightfatty alcohol.

The treatment of leather with aqueous solutions or dis- In general, from1 to 10%, but preferably from 2 in the solution or by brushing orotherwise applying the solution onto the leather.

-After this pro-treatment the leather is impregnated accordingto-theprocedure-described in U.S. Patent No. 'An alcohol solution of anorganometallic complex isdiluted-with'water or anorganic solvent to thedesired concentration andthe leather is'then impregnated with thissolution by any ofthe customary methods.

The impregnating agents are solutions of organometallic complexcompounds which have been obtained byreact- "ing basicpolyvalent'metal-saitswith acid phosphoric acid esters formed with highmolecular weight hydroxyl compounds in the presence of low-molecularweight monovalent alcohols.

These salts are water-miscible, -cationic-active, organic, complex saltsof a polyvalent metal containing aratio of at least 2.5 mols of analcohol-soluble, basic salt of "a polyvalent metal selected from-thegroup consisting of aluminum, chromium, iron, mercury, tin, titanium andzirconium, for every one mol of an acidester of phos phoric acidesterified with an alcohol selected from the group consisting-ofalkanols, alkenols, cycloalkanols, al-

kylphenols and alkylcycloalkanols, said alcohol having about 6 to about18 carbon atoms in the molecule, and having coordinated with said basicsalt and said acid ester a lower alcohol selected from the groupconsisting of lower alkanols, tetrahydrofurfuryl alcohol and 1,2 pro--pylene glycol.

acid ester complexes are formed thereby whichhave a cationic character.Such products are also obtained when .berentirely or partially omitted,depending upon the amount ofqcomplex componnds,used. vFor the process 4the process according to the present application is the subject matterof the copending patent application Serial No. 621,008, filed November8, 1956, now U.S. Patent No. 2,885,417, in the name of one of us. Thestarting materials for the production of these organic complex salts arebasic salts of polyvalent metals formed with inorganic or organic acids;for example, basic chromium chloride, basic aluminum nitrate, basictitanium chloride, etc. Suitable phosphoric acid esters are monoanddiesters of ortho-phosphoric acid; for example, monoor dioctylphosphoric acid ester, monoor didodecyl phosphoric acid ester, monoordioleyl phosphoric acid ester, or esters of other aliphatic,cycloaliphatic, aliphatic-aromatic or cycloaliphatic-aromatic hydroxylcompounds. The starting material may also be an acid ester mixture, suchas is. obtained by a rection of phosphorus pentoxide with high molecularweight hydroxyl compounds. Suitable low molecular .weight monovalentalcohols are primarily methanol and ethanol. The solutions obtainedinthis manner are solutions of metal complex compounds in the lowmolecular weight monovalent alcohols, which may be'diluted to anydesiredextent with water .and are then used in this form for the impregnationof the leather. These complex metal compounds are produced by thereaction under anhydrous conditions at reflux temperatures in theratioof at least 2.5 mols of an alcohol-soluble,

basic .salt of a polyvalent metal selected from the group sisting ofalkanols, alkenols, cycloalkanols, alkylphenols and alkylcycloalkanols,said alcohol having about,6v to about 18 carbon atoms in the molecule.In the produc .tionof the above metal complex compounds it isnotabsolutely, necessary to usethe above-mentionedprocess; instead, vothermethods of producing these compounds may beused, provided that solublemetal alkylphosphoric basic metal salts are reacted with acid alkylphosphates in,the molten state.

Thetreatment of the leather with these solutions proceedsin customaryfashion, such as by immersion, rolling, brushing .or plush-wheeling; or,for example, in

lustering of suede leather, by spraying with the aid of spray guns.Since the complex compounds also possess fattingproperties, thecustomary fat-liquoring agents may according tothe invention about 1,to10%, andpreferably betweeno and 8% by weight of thecomplex compounds,based upon the shaved weight of the leather,';is

required. Porbrushingor spraying it is advantageous to use 5 to15%.,solutions. In place of the aqueous-solutions, solutions inorganicsolvents, such as trichloroethylene, isopropyl alcohol, ,benzene, andthe like may be used.

The, present process may be used for impregnating mineral-tanned,vegetable-tanned, synthetic-tanned, resintanned, formaldehyde-tanned andcombination-tanned leathers,

The advantages of the present process reside inthat the two-stepimpregnation according to ,the invention produces leather'withespecially valuable properties, be cause the pretreatment effects animprovement in the water-impermeability, whereas the subsequenttreatment renders the individual leather fibers water-repellent, so thatthe fibers retain a very low water-absorbing capability. Furthermore,the process produces substantially easier and more rapid impregnation,even in thick leather, with substantially lower requirements ofimpregnating agents. 1 The advantages "of the process according to theinvention make themselves felt especially with combina tion-tannedleather, such as with flexible combination tanned sole leather. Thequality and value of such leather depends substantially upon thewater-impermeability under conditions of ordinary usethat is, underpressurewhich is considerably improved by the present combinedtreatment.

The following examples will further illustrate the pres ent inventionand will enable others skilled in the art to understand it morecompletely. It is not intended, however, to limit the invention to theseparticular examples.

Example I Vache leather or heavy sole leather, which had been pretannedwith 0.5 to 1% chromium oxide and retanned with about 20% vegetabletanning agents, and which had a pH of about 3.8 to 4.2 at the leatheredge, was sammed until it had a water content of about 50 to 60%, andwas then treated with 1.5 to 3% of the ammonium salt of an acidphosphoric acid dodecyl ester and with to 30% water in a hot airchamber. The running time was 30 minutes to 1 hour at a hot air feedtemperature of about 60 C. Subsequent to this treatment the leather edgehad a pH value of 4.5 to 5.0 and toward the end of the treatment wasadjusted with formic acid (about 0.5%) to a value of about 3.5. Theleather was then removed from the bath and stored on the horseovernight. Thereafter the leather was treated in the drum without hotair feed at a temperature of 30 to 40 C. for about 1 hour in a bathcontaining to 30% water and 15 to 25% of a 30% chrome complex saltsolution which was produced as follows:

257 parts by weight of a methanol solution containing 17.5 parts byweight of 33% basic chromium (III) chloride were admixed with a solutionof 14.75 parts by weight of a technical grade alkylphosphoric acid estermixture (alkyl radicals containing 12 to 18 carbon atoms) in 85 parts byweight methanol. The mixture was boiled for 5 hours under reflux andthen a portion of the methanol was distilled off.

Subsequently the leather was bufiered in the same bath with 1.5 to 2.5%sodium bicarbonate (based on the weight of chrome complex salt). Theleather was then rinsed for a short time in a drum. After storage on thehorse overnight, friction glazing and drying at 25 to 30 C., the leatherwas worked up in customary fashion.-

It was advantageous to redry the leather for a short time attemperatures of 50 to 70 C. The impregnation efiect thereby achieved itsmaximum value. When the leather was not redried at the elevatedtemperature, this maximum value was not reached until the storage seasoning of the leather.

Example II Fat-liquored and retanned waterproof leather was treated with1 to 4% of the ammonium salt of a monododecylcitric acid ester and with10 to 30% water. The running time was from 30 minutes to 1 hour underhot air feed in a hot air drum. The leather treated in this manner wasstored on the horse overnight. Thereafter the leather was stuffed, underthe customary conditions in a hot air drum, with a waterproofingcomposition which contained of the complex salt solution according toExample 1.

Example III Chrome tanned and neutralized ASA leather was prefatted andthen treated at suitable fat-liquoring temperatures with 0.5 to 4% basedon the weight of the leathers of a fat-liquoring oil consisting of amixture of 40% sulfonated shark oil, 10% mineral oil. 40% sperm oil and10% of the ammonium salt of an alkyl malonic acid, the alkyl radical ofwhich had a carbon chain of 12 to 18 carbon atoms, this amount of mixedoil was dispersed in about 100%, based on the weight of 1eather,'ofwater.

a esgm The running time was about 30 to 45 minutes. At the end of thisperiod the leather was acidified to a pH of about 3.5 with formic acid.Thereafter the leather was placed on the horse, allowed to remain thereovernight, and was then treated with 10%, based on the weight of theleather, of the about 30% chrome complex salt mentioned in Example I atabout 40 0., this amount of chrome complex salt was dissolved in about50 to of water, based on the weight of the leather. The running time was30 minutes to 1 hour. The leather was then dried and further worked upin customary fashion.

While we have illustrated our invention with various specificembodiments, it will be obvious to persons skilled in the art thatvarious changes and modifications may be made without departing from thespirit of the invention or the scope of the appended claims.

We claim:

1. The method of water-proofing leather which coniprises impregnatingtanned leather with a. water-miscible derivative selected from the groupconsisting of esters, amides and acids of a polybasic acid selected fromthe group consisting of dibasic and higher polybasic organic acids andtribasic and higher polybasic inorganic acids, said derivativecontaining at least one hydrophobic radical and at least twosalt-forming radicals capable of forming complexes and thereafterimpregnating said tanned leather with a water-miscible, cationic-active,organic, com plex salt of a polyvalent metal containing a ratio of atleast 2.5 mols of an alcohol-soluble, basic salt of a polyvalent metal,with one mol of an acid ester of phosphoric acid esterified with analcohol containing a hydrophobic radical, said alcohol having about 6 toabout 18 carbon atoms, and having coordinated with said basic salt andsaid acid ester a lower molecular weight alcohol.

2. The method of water-proofing leather which comprises impregnatingtanned leather with a water-miscible derivative selected from the groupconsisting of esters, amides and acids of a polybasic organic acidcontaining at least two acidic salt-forming groups, said derivativecontaining at least one hydrophobic radical and at least twosalt-forming radicals capable of forming complexes and thereafterimpregnating said tanned leather with a water-miscible, cationic-active,organic, complex salt of a polyvalent metal containing a ratio of atleast 2.5 mols of an alcohol-soluble, basic salt of a polyvalent metalwith one mol of an acid ester of phosphoric acid esterified with analcohol containing a hydrophobic radi cal, said alcohol having about 6to about 18 carbon atoms, and having coordinated with said basic saltand said acid ester a lower molecular weight alcohol.

3. The method of water-proofing leather which comprises impregnatingtanned leather with a water-miscible ester of a polybasic inorganic acidcontaining at least two acidic salt-forming groups, said estercontaining at least one hydrophobic ester radical and at least twosaltforming radicals capable of forming complexes and there afterimpregnating said tanned leather with a water-miscible, cationic-active,organic, complex salt of a polyvalent metal containing a ratio of atleast 2.5 mols of an alcohol-soluble, basic salt of a polyvalent metalwith one mol of an acid ester of phosphoric acid esterified with analcohol containing a hydrophobic radical, said alcohol having about 6 toabout 18 carbon atoms, and having coordinated with said basic salt andsaid acid, ester a lower molecular weight alcohol.

4. The method of water-proofing leather which comprises impregnatingtanned leather with a water-miscible. ester of a polybasic acid selectedfrom the group consisting of dibasic and higher polybasic organic acidsand tribasic and higher polybasic inorganic acids, said ester containingat least one hydrophobic ester radical and at, least two salt-formingradicals capable of forming complexes and thereafter impregnating saidtanned leather with a water-miscible, cationic-active, organic, complexsalt of a polyvalent metal containing a ratio of at least.

2 9 ct analwh lz qlu le, ba i sa tg a p lyva en me a .With one mol of'ana i est O p osp r c' c d esterified with anal'cohol containing ahydrophobic radia 15 lcqh having out o ab u v 8 a bQ atoms and'hav ncoor na wit said asi al n said acid ester a lower molecular weightalcohol.

5. The method of water-proofingdeather which comprises impregnatingtanned leather with a'water-rniscible mid o a po yba c a id sel ct d .fom the up co s st n o diba i d hig p lybas c Organic ci sa amidederivative containing .at least one hydrophobic amide radical and atleast two salt-forming radicals capable of forming complexes andthereafter impregnatn 'sa n ed eath w t a tc kmi ble c t on active,organic, complex salt of a polyvalent metal containing a ratio of atleast 12.5 mols of an alcohol-soluble, basic salt of a polyvalent metalwith one mol of an acid ester of phosphoric acid esterified with analcohol containing a hydrophobic radical, said alcohol having about 6 toabout 18 carbon atoms, and having coordinated with said basic salt andsaid acid ester a lower molecular weight'alcohol.

6; The method of waterproofing leather which comprises impregnatingtanned leather with 1% to 10% by weight, based on the shaved weight ofthe leather of a water-miscible derivative selected from the groupconsisting of esters, amides and acids of a polybasic acid selected fromthe group consisting of dibasic and higher polybasic organic acids andtribasic and higher polybasic inorganic acids, said derivativecontaining at least one hydrophobic radical and at least twosalt-forming radicals capable of forming complexes and thereafterimpregnating said tanned leather with 1% to 10% by weight, based on theshaved weight of the leather of 'a waterm iscible, cationic-active,organic, complex salt of a polyvalent metal containing a ratio of atleast 2.5 mols of an alcohol-soluble, basic salt of a polyvalent metalwith one mol of an acid ester of phosphoric acid esterified with analcohol containing a hydrophobic radical, said alcohol having about 6 toabout 18 carbon atoms, and having coordinated with said basic salt andsaid acid ester 21 lower molecular weight alcohol.

' 7. A process for rendering leather water-proof which comprisestreating the tanned leather with an aqueous solution containing 1% to10% by weight based on the shaved weight of the leather of awater-miscible derivative selected from the group consisting of esters,amides and acids of a polybasic acid selected from the group consistingof dibasic and higher polybasic organic acids and tribasic and higherpolybasic inorganic acids, said derivative containing at least onehydrophobic radical and at least two salt-forming radicals capable offorming complexes for a time sufficient to impregnate the leather andthereafter treating the tanned impregnated leather with a solutioncontaining 1% to 10% by weight based on the shaved weight of the leatherof a water-miscible, cationic-active, organic, complex salt of apolyvalent metal containing a ratio of at least 2.5 mols of analcoholsoluble, basic salt of a polyvalent metal with 'one mol of anacid ester of phosphoric acid esterifiedwith an alcohol containing ahydrophobic radical, said alcohol having about 6 to about 18 carbonatoms, and having coordinated with said basic salt and said acid ester alower molecular weight alcohol, for a time sufficient to impregnate theleather and then drying the leather at elevated temperatures.

8. A process for rendering leather water-proof which comprises treatingthe tanned leather with an aqueous solution containing 1% to 10% byweight based on the shaved weight of the leather of a water-misciblederivative selected from the group consisting of esters, amides andacids of a polybasic organic acid containing at least two acidicsalt-forming groups, said derivative containing at least one hydrophobicradical and at least two saltfgrrning radicals capable of formingcomplexes for a time sufiicientto impregnate the leather and thereaftertreat-V salt of a polyvalent metal with one mol of an acid ester ofphosphoric acid esterified with an alcohol containing a hydrophobicradical, said alcohol having about 6 to about 18 carbon atoms, andhaving coordinated with said basic salt and said acid ester a lowermolecular weight alcohol, for a time sufiicient to impregnate theleather and then drying the leather at elevated temperatures.

9. A process for rendering leather water-proof which comprises treatingthe tanned leather with an aqueous solution containing 1% to 10% byweight based on the shaved weight of the leather of a water-miscibleester of a polybasic inorganic acid containing at least two acidicsalt-forming groups, said ester containing at least one hydrophobicester radical and at least two salt-form ing radicals capable of formingcomplexes for a time suificient to impregnate the leather and thereaftertreating the tanned impregnated leather'with a solution containing 1% to10% by weight based on the shaved weight of the leather of awater-miscible, cationic-active, organic complex salt of a polyvalentmetal containing a ratio of at least 2.5 mols of an alcohol-soluble,basic salt of a polyvalent metal with one mol of an acid ester ofphosphoric acid esterified with an alcohol containing a hydrophobicradical, said alcohol having about 6 to about 18 carbon atoms, andhaving coordinated with saidbasic salt and said acid ester a lowermolecular weight alcohol, for a time sufficient to impregnate theleather and then drying the leather at elevated temperatures.

10. A process for rendering leather water-proof which comprises treatingthe tanned leather with an aqueous solution containing 1% to 10% byweight based on the shaved weight of the leather of a water-miscibleester of a polybasic acid selected from the group consistingof dibasicand higher polybasic organic acids and tribasic and higher polybasicinorganic acids, said ester contain ing at least one hydrophobic esterradical and at least two salt-forming radicals capable of form-ingcomplexes for a time sufiicient to impregnate the leather and thereaftertreating the tanned impregnated leather with a solution containing 1% to10% by weight based on the shaved weight of the leather of awater-miscible, cationicactive, organic, complex salt of a polyvalentmetal containing a ratio of at least 2.5 mols of an alcohol-soluble,basic salt of a polyvalent metal with one mol of an acid ester ofphosphoric acid esterified with an alcohol containing a hydrophobicradical, said alcohol having about 6 to about 18 carbon atoms, andhaving coordinated with said basic salt and said acid ester a lowermolecular weight alcohol, for a time sufiicient to impregnate theleather and then drying the leather at elevated temperatures.

11. A process for rendering leather Water-proof which comprises treatingthe tanned leather with an aqueous solution containing 1% to 10% byweight based on the shaved weight of the leather of a Water-miscibleamide of a polybasic acid selected from the group consisting of dibasicand higher polybasic organic'acids, said amide containing at least onehydrophobic amide radical and at least two salt-forming radicals'capableof forming complexes for a time sufficient to impregnate the leather andthereafter treating the tanned impregnated leather with a solutioncontaining 1% to 10% by Weight based on the shaved weight of the leatherof a water-miscible, cationic-active, organic, complex salt of apolyvalent metal containing a ratio of at least 2.5 mols of analcoholsoluble, basic salt of a polyvalent metal with one mol of an acidester of phosphoric acid esterified with an alcohol containing ahydrophobic radical, said alcohol having from about 6 to about 18 carbonatoms, and having coordinated with said basic salt and said acid ester alower molecular weight alcohol, for a time sufiicient to impregnate theleather and then drying the leather at elevated temperatures.

12. The process of claim 10 wherein said water-miscible ester of apolybasic acid is an ammonium salt of an acid phosphoric acidmonododecyl ester.

13. The process of claim 10 wherein said water-miscible ester of apolybasic acid is an ammonium salt of the monododecyl citric acid ester.

14. The process of claim 8 wherein said water-miscible derivativeselected from the group consisting of 10 esters, amides and acids of apolybasic organic acid is an ammonium salt of an alkyl-malonic acid,said alkyl radical containing 12 to 18 carbon atoms.

References Cited in the file of this patent UNITED STATES PATENTS2,372,985 Roth Apr. 3, 1945 2,693,996 Von Fuchs Nov. 9, 1954 2,772,988Plapper et a1 Dec. 4, 1956 FOREIGN PATENTS 541,861 Canada June 4, 1957

1. THE METHOD OF WATER-PROOFING LEATHER WHICH COMPRISES IMPREGNATINGTANNED LEATHER WITH A WATER-MISCIBLE DERIVATIVE SELECTED FROM THE GROUPCONSISTING OF ESTERS, AMIDES AND ACIDS OF A POLYBASIC ACID SELECTED FROMTHE GROUP CONSISTING OF DIBASIC AND HIGHER POLYBASIC ORGANIC ACIDS ANDTRIBASIC AND HIGHER POLYBASIC INORGANIC ACIDS, SAID DERIVATIVECONTAINING AT LEAST ONE HYDROPHOBIC RADICAL AND AT LEAST TWOSALT-FORMING RADICALS CAPABLE OF FORMING COMPLEXES AND THEREAFTERIMPREGNATING SAID TANNED LEATHER WITH A WATER-MISCIBLE, CATIONIC-ACTIVE,ORGANIC, COMPLEX SALT OF A POLYVALENT METAL CONTAINING A RATIO OF ATLEAST 2.5 MOLS OF AN ALCOHOL-SOLUBLE, BASIC SALT OF A POLYVALENT METAL,WITH ONE MOL OF AN ACID ESTER OF PHOSPHORIC ACID ESTERIFIED WITH ANALCOHOL CONTAINING A HYDROPHOBIC RADICAL, SAID ALCOHOL HAVING ABOUT 6 TOABOUT 18 CARBON ATOMS, AND HAVING COORDINATED WITH SAID BASIC SALT ANDSAID ACID ESTER A LOWER MOLECULAR WEIGHT ALCOHOL.